Despite some recent concerns about the environmental fate of halogenated polymers, polyvinyl chloride (PVC) still remains one of the major commodity polymers produced and consumed worldwide. This is primarily due to the low cost to produce and process PVC as well as the ability to form PVC products having a wide range of material properties (from flexibly to rigid). Recent life-cycle studies have shown that vinyl products perform very favorably in terms of energy efficiency, have high thermal insulating value, low contribution to greenhouse gas production, are low maintenance and have outstanding product durability. However like most commodity polymers, PVC is made from 100% petroleum-based feedstocks and is therefore not environmentally sustainable.
Because of PVC's poor thermal stability, stiffness and propensity for brittle fracture, it needs to be compounded with a significant amount of additives such as processing aids, heat stabilizers, plasticizers and impact modifiers in order to make useful products. Polyvinylchloride is usually plasticized to achieve flexibility however plasticization can adversely affect other PVC material properties such as impact strength and tensile toughness. A material property balance must be achieved therefore when formulating with plasticizers. Plasticizers properties such as miscibility are very important in enhancing PVC property performance. If plasticizers are not miscible and are of low molecular weight, they tend to migrate to the surface of the PVC and are then easily removed by extraction or volatilization which leads a loss of properties for the PVC product.
To mitigate PVC property changes when formulating with plasticizers, it is common to add rubbery polymeric impact modifiers to improve the toughness of PVC compounds. These impact modifiers however are often not miscible with PVC and require a grafted polymeric outer layer which is able to adhere to the PVC matrix while being chemically bonded to a rubbery polymeric core. It is the rubbery core which is able to dissipate the energy of impact. These types of impact modifiers are often not UV and/or oxidative stable and therefore require additional UV and antioxidant stabilizers when used in compositions. Formulation with the PVC then becomes very complex. Therefore a need exists for miscible, stable and easy to handle polymeric modifiers or additives for PVC that have good short and long term, thermal, UV and oxidative stability but provide good impact and/or plasticizing properties.